Servo valve troubleshooting

The failure of the servo valve is often found when the electro-hydraulic servo system is commissioned or not working properly. So sometimes there are system problems including malfunctions such as amplifiers, feedback mechanisms, and actuators. Sometimes it is a servo valve problem. So first of all, it must be clear whether it is a system problem or a servo valve problem. The common way to solve this problem is: First, the valve is unloaded conditionally, and the test bench can be retested. Second, most of the conditions without this condition, then a simple way is to open the system, standby independent DC power supply, after the multimeter to the servo valve for different positive and negative value current, from the valve output to determine whether the valve What is wrong with you? Valve problem is not large, then look for system problems, such as: Excessive internal leakage of the actuator will cause the system to slow down, serious hysteresis, or even not work; the feedback signal is broken or abnormal, etc., the amplifier problem has an output signal distortion or Do not work, system problems here ominous talk, the following mainly talk about valve failure.

(1) The valve does not work because: The motor coil is disconnected, and it is desoldered; there are oil inlets or outlets. Another possibility is that the pre-stage blockage causes the spool to be stuck in the middle dead zone. This is of course less likely that the spool is stuck in the middle. The two coils of the motor coil are connected in series or in parallel, and the magnetic force formed by the two coils just cancels out.

(2) The valve has a fixed output, but the reason has been out of control: the prepositioned nozzle is blocked, the valve plug is stuck on the stolen object and the valve body is deformed to cause the spool to jam, or the internal protection filter is blocked by the stolen material. To replace the filter, return to the factory for cleaning and repair.

(3) Responsiveness of valve response, slow response, etc. Reasons: There is a decrease in the system oil supply pressure, a partial blockage of the protection filter, loosening of some valve zero adjustment mechanisms, loosening of other parts of the motor, or a moving coil of the dynamic ring valve and the control valve core Loosening. Excessive leakage of power elements in the system is another reason. In addition, the oil is too dirty, the valve resolution becomes worse, and hysteresis widening is also one of the reasons.

(4) The system has a high frequency of vibration and noise reasons: the amount of air mixed in the oil is too large, the oil is too dirty; the system gain is adjusted too high, the power supply noise from the amplifier, the servo valve coil and the valve housing and ground The line insulation is not good, is a non-pass, flutter signal is too large or resonant phenomenon caused by the system frequency relationship, and then a relatively low system and chose a servo valve of high frequency.

(5) The output of the valve is suddenly positive and negative, and it cannot be controlled continuously. It becomes a "switch" control.

Cause: The feedback mechanism in the servo valve fails, or the system feedback is disconnected, or some positive feedback phenomenon occurs.

(6) Oil leakage reasons: The surface quality of the mounting seat is not good and the seal cannot be sealed. Valve sealing ring quality problems, seals on valve plugs, etc. are damaged. If the oil leaks between the motor cover and the valve body, the spring tube may be broken and the internal oil pipe may be broken.

Servo valve troubleshooting, and some can be ruled out, but many faults to the valve to the production plant, put on the test bench to repair and re-emphasize, and then stressed again: Do not own valve, it is very easy to damage the servo valve parts.

With the servo valve more units can install a simple test bench to determine whether the problem is the system or the valve, the valve has any problems, can be reused.